The trick is to calculate how many mg makes a kg.
Since 1 Kg = 1000000 mg
Then it follows that 1.2 Kg will yield
1 Kg = 1000000 mg
1.2 kg = X
X = 1200000 mg
So 1.2 kg contains 1200000 mg
Hence we can get 1200000/ 81 = 14814.814.
There are 14, 814 low dose